Skin and hair

This covers appearance-level outcomes: skin texture and fine lines, wound and scar appearance, pigmentation, hair density. The single most useful thing to know before comparing anything on the list is that most of these compounds have their best evidence applied to the skin rather than injected into it — and topical and systemic use are not interchangeable claims.

GHK-Cu leads at 5. It is a copper-binding tripeptide with small human cosmetic studies of topical formulations at roughly 0.05 to 2 per cent; the injectable use and the one-to-two milligram figures come from community protocols and animal wound-healing data rather than controlled trials. Melanotan II at 4 is a different proposition entirely — a non-selective melanocortin agonist that drives pigmentation, is not approved in any country, never completed phase 3 development, and is sold as unlicensed material of unverified purity. KPV and LL-37 at 3 address inflammatory skin and wound healing; epitalon, MK-677 and TB-500 sit at 2.

Where a topical route exists, start there: it is where the evidence is and it removes most of the systemic exposure. Cycle GHK-Cu rather than running it continuously, because the copper load is the reason for the cycling convention. And if you are seriously considering Melanotan II, the mole check belongs before the first dose rather than after — driving melanogenesis while carrying unmapped naevi is the specific risk, and no cosmetic outcome offsets it casually.